JP2001342384A - Thermal transfer recording liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise print concentration and to prolong a print life. SOLUTION: Dodecachloropentacyclooctadecadiene or tricresyl phosphate described by formulas 1 and 2 is added as an additive to the liquid. This achieves necessary and sufficient print density in a printing process that uses a recording device of the thermal transfer printing type. This also extends the life of the print and reduces the power to be consumed in the printing process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording liquid used in a printer for recording information such as characters and images on a transfer medium such as photographic paper. More particularly, the present invention relates to a thermal transfer recording liquid used in a printer that performs recording by flying the thermal transfer recording liquid by holding the thermal transfer recording liquid in an ink transfer section and heating the ink by a heating unit.

[0002]

2. Description of the Related Art In recent years, the need for colorization of printers for individuals or small offices called "small office home offices" has been rapidly increasing. In response to this, color hard copy systems such as a sublimation thermal transfer system, a melt thermal transfer system, an on-demand inkjet system, and an electrophotographic system have been proposed.

[0003] Items required for the above-mentioned printers are to satisfy image quality comparable to silver halide photography, to output an A6 size image within 10 seconds (6 ppm or more), and to reduce the running cost of silver halide photography. And that the device cost is within 100,000 yen.
However, a printer satisfying all of the above requirements has not been realized yet.

In order to realize a printer satisfying the above requirements, various new thermal transfer systems have been proposed. One of them is disclosed in, for example, JP-A-9-183.
No. 239 and Japanese Patent Application Laid-Open No. 9-183246 have been proposed.

In this method, a thermal transfer recording liquid, ie, ink, is heated in a transfer section of a printer head to cause the ink to fly as gaseous droplets or fine droplets having a diameter of 20 μm or less. 300
Transfer is performed by adhering to the surface of a transfer-receiving body such as printer paper that is opposed to each other with a gap of about μm.

The transfer portion is provided with an ink holding structure having an uneven structure in which, for example, a large number of pillars having a width or diameter of about 2 μm and a height of about 6 μm are arranged upright at a very small interval of about 2 μm. A heater is provided below the holding structure to form a transfer unit.

By providing such an ink holding structure in the transfer section, the following effects can be obtained.

(1) Ink is spontaneously supplied to the transfer section by capillary action.

(2) Due to the large surface area, the ink can be efficiently heated.

(3) By appropriately setting the height of the columnar body, a predetermined amount of ink can always be held in the transfer section.

(4) Since the surface tension of the liquid generally has a negative temperature coefficient, the locally heated ink is subjected to a force directed to the outer peripheral portion having a low temperature, but its movement is minimized by the ink holding structure. , And a decrease in transfer sensitivity is prevented.

Accordingly, by providing such an ink holding structure, it is possible to fly an amount of ink corresponding to the heating at the transfer section and transfer it to printer paper or the like. That is, the density gradation in the pixel becomes possible. As a result, for example, a high-quality image comparable to a silver halide color photograph can be obtained.

Further, since it is not necessary to use an ink ribbon or the like, the running cost is reduced. In addition, it is possible to transfer to plain paper or very inexpensive recording paper equivalent to plain paper by using ink with good absorbency for plain paper or coating ink receiving layer on plain paper. Therefore, this also lowers the running cost.

In addition, since this method utilizes flying by thermal action on ink, the transfer portion of the printer head that heats the ink must of course be pressed against a transfer target such as printer paper with a high pressure. No need to contact. Therefore, there is no problem of thermal fusion between an ink heating unit such as an ink ribbon and a printer paper, which may occur in other thermal transfer systems.

That is, according to this thermal transfer recording system,
As with the dye diffusion thermal transfer method described above, it is possible to reduce the size and weight of the printer, and at the same time, it is possible to reduce waste and reduce running costs due to the absence of an ink ribbon or the like. Further, according to this thermal transfer method, ease of maintenance and immediacy at the time of printing and high quality of the printed image are guaranteed, and at the same time, power consumption is reduced and plain paper is used. Cost reduction is also possible.

[0016]

In the thermal transfer recording system as described above, ink and photographic paper used for the printer and the thermal transfer system are being developed.

In JP-A-9-183239 and JP-A-9-183246, the dye of the ink used in the thermal transfer recording system is required to have a predetermined boiling point and to have a necessary and sufficient density. It is stated that oil-soluble dyes, especially disperse dyes, are preferred because they have advantages.

However, when the ink described in the above-mentioned publication is used, in order to obtain a necessary and sufficient print density,
A lot of energy, that is, electric power was required at the time of printing. Further, it was difficult to obtain a sufficient printing density, and at the same time, the printing life was insufficient.

The present invention has been made in view of such a conventional situation, and enables printing with low power and excellent density in a thermal transfer recording system.
An object of the present invention is to provide a thermal transfer recording liquid having a long printing life.

[0020]

The thermal transfer recording liquid is prepared by mixing a dye and a solvent, and to which additives are added if necessary. As a result of intensive studies, the inventors have found that the addition of dodecachloropentacyclooctadecadiene or the like enables excellent printing in a thermal transfer recording system.

The thermal transfer recording liquid according to the present invention is characterized in that it contains a solvent, a dye, and dodecachloropentacyclooctadecadiene represented by the following formula (4) or tricresyl phosphate represented by the following formula (5). I do.

[0022]

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[0023]

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Therefore, the thermal transfer recording liquid according to the present invention has a good print density and a sufficiently long print life when printing is performed using a thermal transfer printing type printer. Also, the energy consumed by the printer during printing is reduced.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal transfer recording liquid to which the present invention is applied will be described below in detail with reference to FIGS.

First, the thermal transfer recording liquid, that is, ink, to which the present invention is applied will be described.

The ink according to the present invention includes a heater chip provided on a base plate, a heating means formed on the heater chip, and one or more lines arranged on the heater chip in a longitudinal direction of the heater chip. A transfer portion having a concave-convex structure, wherein the ink held in the transfer portion by capillary action is heated by a heating means according to information to be recorded, whereby the ink is transferred in a gaseous and / or liquid form. This is used for a so-called thermal transfer recording type printer which flies toward a body and transfers information to a body to be transferred. That is, the above-described ink is used by being housed in a so-called thermal transfer recording type printer head.

Here, the “flying” means vaporization, evaporation, or the like occurring due to heating by a heating means such as a heater.
And flying the ink by convection of the ink. The causes of the convection of the ink described above are that the surface tension of the ink liquid surface is uneven, the volume of the ink expands due to the boiling of the components constituting the ink, and that the dissolved air in the ink expands. , The thermal expansion of the ink, and the thermal expansion of the heater or capillary structure.

The ink to which the present invention is applied is composed of a pigment (dye or pigment), a solvent, and an additive. Pigment,
The solvent and the additives are determined in such a manner that the transfer temperature, the thermal stability, the image quality, and the storage stability of the image to be printed by the printer 1 are optimized, and the material and the component composition ratio are determined.

In the present invention, dodecachloropentacyclooctadedecadiene or tricresyl phosphate as shown in the following chemical formulas 6 and 7 is added to the ink.

[0031]

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[0032]

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As a result, when printing is performed using a printer of a thermal transfer recording system, a necessary and sufficient printing density is obtained and the printing life is increased. The printing life is
It means the number of times that printing can be performed with a necessary and sufficient printing density.

Further, other additives may be added as needed to adjust the physical properties of the ink. Such additives include surfactants, viscosity modifiers, preservatives and the like. These additives have a similar boiling point as the solvent and the dye. Specifically, as a surfactant,
Fluorinated fatty acid esters, silylated fatty acid esters, silicon oil and the like can be used. In addition, glycerin, tetraethylene glycol, or the like can be used as a viscosity modifier.

The dye must satisfy the conditions that it has sufficient heat resistance, that it is sufficiently soluble in the solvent described below, that it has sufficient storage stability on photographic paper, and that it has low toxicity to the human body. Any compound can be used as long as it is used.

Specifically, it is preferable to use disperse dyes, oil-soluble dyes, basic dyes, and the like as the pigment. It is more preferable to use an anthraquinone-based dye such as an anthraquinone-based magenta dye and an anthraquinone-based cyan dye described in JP-A-8-244366. When using an anthraquinone dye,
By adding dodecachloropentacyclooctadecadiene or tricresyl phosphate, the printing density increases and the printing life is prolonged.

These dyes are used in sublimation purification method, recrystallization method, zone melting method, column purification method and the like in order to reduce the evaporation residue and prevent the thermal decomposition product from adhering to the recording part. It is desirable to use it after purification by the method. These dyes may be used as a mixture of two or more kinds in order to improve the solubility in a solvent described below.

These dyes are used in an amount of 5
It is preferred that the content be contained by weight% or more. Further, the content is more preferably 10% by weight or more, and most preferably 20% by weight or more, based on the solvent described below.

As the solvent, any compound may be used as long as it has a melting point of less than 50 ° C., a high thermal decomposition temperature, a high compatibility with the dye, a colorless color, and a low toxicity to the human body. Can be.

Specifically, phthalic esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, dioctyl phthalate, diisodecyl phthalate, dibutyl sebacate, dioctyl sebacate, dioctyl adipate, Fatty acid dibasic acid esters such as diisodecyl adipate, dioctyl azelate, dioctyl tetrahydrophthalate, phosphates such as tricresyl phosphate and trioctyl phosphate, and tributyl acetylcitrate and butylphthalylbutyl glycolate, Organic compounds generally referred to as plasticizers for plastics can be used.
Further, diethylene glycol, diethylene glycol dibutyl ether, diethyl ether and the like can also be used.

Further, two or more of the above compounds may be mixed to form a solvent. The solvent preferably contains diethylene glycol dibutyl ether as shown in the following Chemical Formula 8. By including diethylene glycol, the printing density is high and stable.

[0042]

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As the solvent, it is desirable to use a lipophilic compound as described above, but it is also possible to use water or glycol.

Next, a printing paper suitable for printing by a printer having the above-described ink will be described.

Printing paper suitable for this recording method is P
Plain paper such as PC paper and high quality paper such as art paper can be used. In order to obtain a high-quality image with particularly high gradation and density, polyester, polycarbonate, acetate, cellulose acetate butyrate (C) is used as a resin for coloring a disperse dye or an oil-soluble dye.
AB), polyvinyl chloride, or the like, and a special paper produced by coating the substrate on the substrate can also be used.

In order to improve the ink absorption speed,
A porous pigment such as silica or alumina is added. In particular, from the viewpoint of high-quality recording, for example, in terms of smoothness, color development, gloss, and ink absorption speed, a size of 0.1 μm or less for imparting gloss to a film base such as a polyethylene terephthalate (PET) film. The photographic paper having the image receiving layer to which the porous pigment is added is excellent.

In order to improve the storage stability of the transferred image, an effect can be obtained by adding an additive such as an ultraviolet absorber or a radical quencher to the image receiving layer. It is also effective to laminate a resin film on the photographic paper after transfer.

As is clear from the above description, the ink to which the present invention is applied can be used in a thermal transfer recording type printer by adding dodecachloropentacyclooctadecadiene or tricresyl phosphate as an additive. When printing is performed, a necessary and sufficient printing density can be obtained. In addition, when the ink to which the present invention is applied is used in a printer of a thermal transfer recording system to perform printing, the printing life can be increased and the power consumed by the printer can be reduced.

Next, the printer 1 using the above-described ink will be described. The printer 1 employs a thermal transfer recording method.

The printer 1 includes a paper feed mechanism 2 and an image recording device 3, as shown in FIG.

The paper feed mechanism 2 includes a paper tray 10 for storing photographic paper 4, a paper feed roller 11 for supporting the photographic paper 4 stored in the paper tray 10 so as to sandwich the photographic paper 4, and supplying the photographic paper 4 to a printer head described later. The apparatus includes a platen roller 12 for feeding the printing paper 4 supplied to one printer head and supplying the printing paper 4 to the next printer head, and a paper discharging roller 13 for discharging the printing paper 4 printed by the printer head. The surface of the platen roller 12 in the present embodiment is formed of silicon rubber and has a diameter of 16 mm.

The image recording device 3 includes a platen roller 1
Printer heads 20Y, 20M, 20C (hereinafter, printer head 2)
0. ), A cooling fin 21 for cooling the printer head 20, and an ink tank 22 for storing ink.
And a flexible harness 23 for supplying a signal such as a drive pulse for heating a heater chip provided in the printer head 20 as described later.

In the printer 1 described above, first, the photographic paper 4 is taken out of the paper tray 10 by the paper feed roller 11 and supplied to the printer head 20Y. Then, the ink flies from the printer head 20Y to the printing paper 4. In this embodiment, the printer head 20Y
The color of the ink flying from is assumed to be yellow. Next, the printing paper 4 is supplied from the printer head 20Y to the printer head 20M by the platen roller 12. Then, the ink flies from the printer head 20M to the printing paper 4. In the present embodiment, the color of the ink flying from the printer head M is magenta. Next, the printing paper 4 is transferred to the printer head 20 by the platen roller 12.
M to the printer head 20C. Then, the ink flies from the printer head 20C to the printing paper 4.
In the present embodiment, the color of the ink flying from the printer head C is cyan. The printing paper 4 thus printed is discharged by the paper discharge roller 13 to the printer 1.
Is discharged to the outside. The printer head 20 is maintained at a constant temperature by the cooling fins 21 and a heater described later.

Hereinafter, the printer head 20 will be described in detail. The printer head 20 includes a base plate 30 and a heater chip 31 as shown in FIG.
, Recording unit 32, edge 33, driver IC 34
, An ink passage 35, and a cover 36. Also,
The printer head 20 is connected to a head driving circuit (not shown) via a flexible harness 23.

The base plate 30 is formed with a recording portion 32 for introducing ink into the printer head 20 and a groove for escaping an excess adhesive which sticks out when the heater chip 31 is attached to the base plate 30. I have.
The base plate 30 is formed of, for example, aluminum. The base plate 30 also serves as a heat sink.

The heater chip 31 is formed integrally with a transfer section heated by a heater in accordance with image information and an ink introduction path for guiding ink to the transfer section by capillary action. In the heater chip 31, a plurality of heaters for heating ink, wirings for applying a signal voltage based on an image signal to each heater and energizing the same, and the above-described ink introduction path are formed by a lithography process. Is formed.

A plurality of recording sections 32 are formed at the tip of the heater chip 31, and fly the ink on the printing paper 4. The recording unit 32 has a heater (not shown) one by one. In the present embodiment, the recording unit 32
Are formed at equal intervals at 1216 locations at 300 dpi.

The edge 33 is a portion where the photographic paper 4 contacts. Thus, the angle between the printing paper 4 and the heater chip 31 is appropriately fixed, and the gap between the printing paper 4 and the heater chip 31 is maintained. In this embodiment, the printing paper 4
The gap between the heater and the heater chip 31 was set to 160 μm, and the distance between the recording section 32 and the edge 33 was set to 200 μm.

The driver IC 34 is a section for supplying a heater drive pulse to the heater of each heater chip 31.
It is the flexible harness 23 that supplies the driver driving pulse to the driver IC 34.

The ink passage 35 supplies the ink supplied from the ink tank 22 to each recording unit 32. The ink passage 35 is formed on the base plate 30 and is covered and protected by a cover 36.

The movement of ink in the printer head 20 described above is as follows. First, ink tank 2
After the ink supplied from 2 passes through the ink passage 35, it passes through the gap between the heater chip 31 and the cover 36, and is supplied to the ink introduction path in the heater chip 31. Next, ink is guided from the ink introduction path to the transfer section by capillary action. Then, ink is supplied from the transfer unit to the recording unit 32, and the ink is discharged from the recording unit 32 onto the photographic paper 4.

The transmission of the driving pulse of the heater in the above-described printer head 20 is as follows. First, a driving pulse as shown in FIG.
1 is transmitted to the heater provided in the apparatus. The ink is heated by heating the transfer unit, and the heated ink flies from the recording unit 32 onto the printing paper 4.
The driving pulse shown in FIG. 3 has a duty of 80%
, A short rectangle, and 50 kHz. The heater is heated periodically by such a drive pulse, and the ink in the transfer portion is overheated.

[0063]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The printing density and the printing life of the ink to which the present invention is applied will be described below based on examples.

Example 1 First, the ink was prepared. First, 99.89% by weight of diethylene glycol dibutyl ether and 0.11% by weight of dodecachloropentacyclooctadecadien were mixed to prepare a solvent. Next, a dye in which the amino group of the anthraquinone cyan dye was substituted with a butyl group was purified by a column. Next, 90 parts by weight of the above-described solvent and 10 parts by weight of the purified dye were mixed. Then, the mixture was stirred with an ultrasonic stirrer until the dye was completely dissolved, thereby producing a cyan ink.

Next, the produced ink was introduced into a cartridge of a printer head. At this time, the ink reached the pillar structure of the recording portion by capillary action and formed a meniscus. The thickness of the ink surface at the center of the heater is 6 μm
Met.

Next, as shown in FIG. 3, the rectangular heater 5 with a duty of 80% is applied to the heater of the printer head.
A drive pulse of 0 kHz was applied to periodically heat the ink in the transfer section. This drive pulse was applied to one pixel at most 255 times in accordance with image data. The time (cycle) for forming one pixel, which is obtained by adding the drive pulse application time (255 × 20 μsec = 5.1 msec) and the rest time 0.9 msec for restoring the ink level, is 6 msec (16 msec).
7 Hz). The applied power was 130 mW per heater.

By applying the continuous drive pulse to the heater, the ink in the transfer section is ejected as a mist or fog of about 0.11 pl at the maximum, flies through a gap of 100 μm and adheres to the photographic paper. The ink adhering to the photographic paper immediately absorbed and developed color. Since the pulse application time is very short, the capillary effect due to the column structure of the printer head occurs every time (period) for forming one pixel, so that the ink liquid level completely returns to the initial state and the next pixel is printed. it can.

At this time, the printing paper has a surface of several μm.
Peach coated paper (manufactured by Nisshinbo) having a porous structure described above and using a binder resin compatible with an oil-soluble dye and a solvent was used.

With respect to the printing results obtained above, the printing density was measured using a Macbeth densitometer TR-924 (trade name, manufactured by Macbeth). The printing life was measured by counting the number of printings until the printing density reached 50% of the maximum density.

Example 2 As the dye, an anthraquinone-based magenta dye in which the amino group was substituted with a butyl group was used. Other than that, an ink was produced in the same manner as in Example 1 and introduced into the cartridge of the printer head, and the print density and print life were measured. The power to be applied is 13 per heater.
0 mW.

Example 3 As a dye, a tricyanostyryl-based magenta dye having an amino group substituted with a butyl group was used. Other than that, an ink was produced in the same manner as in Example 1 and introduced into the cartridge of the printer head, and the print density and print life were measured. The applied power is 11 per heater.
0 mW.

Example 4 A solvent was prepared by mixing 95% by weight of diethylene glycol dibutyl ether and 5% by weight of tricresyl phosphate. Other than that, an ink was produced in the same manner as in Example 1 and introduced into the cartridge of the printer head, and the print density and print life were measured. The applied power was 140 mW per heater.

Example 5 As the dye, an anthraquinone cyan dye in which the amino group was substituted with a butyl group was used. Other than that, an ink was prepared in the same manner as in Example 4 and introduced into the cartridge of the printer head, and the print density and print life were measured.
The applied power is 140 mW per heater.
And

Example 6 As a dye, a tricyanostyryl-based magenta dye obtained by substituting an amino group with a butyl group was used. Other than that, an ink was prepared in the same manner as in Example 4 and introduced into the cartridge of the printer head, and the print density and print life were measured. The applied power is 13 per heater.
0 mW.

Comparative Example 1 Diethylene glycol dibutyl ether was used as a solvent, and dodecachloropentacyclooctadecadiene was not added. Other than that, an ink was produced in the same manner as in Example 1 and introduced into the cartridge of the printer head, and the print density and print life were measured. The applied power was 130 mW per heater.

Comparative Example 2 An anthraquinone cyan dye in which the amino group was substituted with a butyl group was used as the dye. Other than that, an ink was prepared in the same manner as in Comparative Example 1 and introduced into a cartridge of a printer head, and the print density and print life were measured.
The power to be applied is 130 mW per heater.
And

Comparative Example 3 A tricyanostyryl magenta dye in which the amino group was substituted with a butyl group was used as the dye. Other than that, an ink was produced in the same manner as in Comparative Example 4 and introduced into a cartridge of a printer head, and the print density and print life were measured. The applied power is 11 per heater.
0 mW.

The results for Examples 1 to 6 and Comparative Examples 1 to 3 are shown in FIGS.

As shown in FIGS. 4 and 5, when an anthraquinone-based cyan ink is used, if dodecachloropentacyclooctadecadien is added, the printing density becomes about 2.0 times and the printing life becomes 1.2 times. became. Also,
When tricresyl phosphate was added, the printing density was about 1.2.
The printing life was approximately tripled.

As shown in FIGS. 6 and 7, when an anthraquinone-based magenta ink is used, if dodecachloropentacyclooctadecadiene is added, the printing density becomes about 1.7 times and the printing life is 1. 7 times. When tricresyl phosphate was added, the printing density was about 1.6 times and the printing life was about 4 times.

As shown in FIGS. 8 and 9, when a tricyanostyryl-based magenta ink was used, when dodecachloropentacyclooctadecadien was added, the printing density hardly changed, and the printing life was about 1
/ 2 times. When tricresyl phosphate was added, the printing density was about 1.1 times and the printing life was about 1.1 times.

[0082]

As is clear from the above description, the thermal transfer recording liquid to which the present invention is applied has the following chemical formula as an additive.
By adding dodecachloropentacyclooctadecadiene or tricresyl phosphate as shown in Chemical formula 10, it is possible to obtain a necessary and sufficient print density when printing using a thermal transfer recording type printer. it can.

[0083]

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[0084]

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The thermal transfer recording liquid to which the present invention is applied is
The printing life when printing is performed using a printer of the thermal transfer recording system is increased, and at the same time, the power consumed by the printer can be reduced.

Therefore, according to the present invention, high-quality printing with low power and excellent printing density can be performed in printing by a thermal transfer printing type printing apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view illustrating a recording apparatus of a thermal transfer system.

FIG. 2 is a schematic perspective view of a printer head in the recording apparatus.

FIG. 3 is a diagram showing driving pulses applied to a heater of a printer head in the recording apparatus.

FIG. 4 is a diagram showing a change in print density when dodecachloropentacyclooctadecadiene or tricresyl phosphate is added to an anthraquinone cyan ink.

FIG. 5 is a graph showing a change in print life when dodecachloropentacyclooctadecadiene or tricresyl phosphate is added to an anthraquinone-based cyan ink.

FIG. 6 is a graph showing a change in print density when dodecachloropentacyclooctadecadiene or tricresyl phosphate is added to an anthraquinone-based magenta ink.

FIG. 7 is a graph showing a change in print life when dodecachloropentacyclooctadecadiene or tricresyl phosphate is added to an anthraquinone-based magenta ink.

FIG. 8 is a diagram showing a change in printing density when dodecachloropentacyclooctadecadiene or tricresyl phosphate is added to a tricyanostyryl-based magenta ink.

FIG. 9 is a graph showing a change in printing life when dodecachloropentacyclooctadecadiene or tricresyl phosphate is added to a tricyanostyryl-based magenta ink.

[Explanation of symbols]

1 printer, 2 paper feed mechanism, 3 image recording device, 10 paper tray, 11 paper feed roller, 12 platen roller, 13 paper discharge roller, 20 printer head, 21 cooling fin, 22 ink tank, 23 flexible harness, 30 base plate, 31 heater chip, 32 recording section, 33 edge, 34 driver IC, 35 ink passage, 36 cover

Claims (4)

[Claims] 1. A thermal transfer recording liquid comprising a solvent, a dye, and dodecachloropentacyclooctadecadiene represented by the following chemical formula 1, or tricresyl phosphate represented by the following chemical formula 2. Embedded image Embedded image 2. The information is recorded on the transfer object by being held by an ink transfer section having an uneven structure by capillary action, heated by heating means in accordance with the information to be recorded, and flying on the transfer object. 2. The thermal transfer recording liquid according to claim 1, wherein the thermal transfer recording liquid is used in a printer that performs the printing. 3. The thermal transfer recording liquid according to claim 1, wherein the dye is an anthraquinone-based substance. 4. The thermal transfer recording liquid according to claim 1, wherein the solvent contains diethylene glycol dibutyl ether represented by the following chemical formula (3). Embedded image